Chapter 2: Atoms, Molecules and Water Flashcards
What is the difference between acid and base in respect to chemical formulas?
H+ (hydrogen ions) is a property of acids, and OH- (hydroxide ions) is a property of bases.
What are the smallest units of matter?
atoms
What charges do the three subatomic particles of an atom have, and where are they located?
Protons are positively charged, located in the nucleus. Neutrons are electrically neutral, located in the nucleus. Electrons are negatively charged, located in orbitals around the nucleus.
T or F. Electrons and neutrons are present in equal numbers, giving the atom a no net charge.
False; electrons and PROTONS are present in equal numbers, giving the atom a no net charge.
How are orbitals organized?
They are organized into electron shells; first shell contains one orbital (max of 2e-), whereas second shell contains 4 orbitals (max of 8e-)
What are valence electrons?
electrons in the OUTERMOST shell; which can participate in the formation of chemical bonds
What distinguishes one element from another?
the number of protons
How do you know if two elements have similar properties?
Both elements are within the same column and have the same number of electrons in their valence shell
How can you determine the atomic mass of an element?
Add the number of protons and neutrons. Ex: 5 protons and 4 neutrons; atomic mass=9.
What are isotopes?
Elements that exist in different forms, that differ in the number of neutrons they contain.
What elements make up 95% of an organisms’ mass?
oxygen, carbon, hydrogen, and nitrogen
How do covalent bonds form?
They form when atoms share a pair of electrons.
T or F. Covalent bond are weak bonds.
False; covalent bonds are STRONG bonds.
How many covalent bonds can carbon form?
4
What is electronegativity?
the ability of an atom to attract electrons
In order to determine if a covalent bond is polar or non-polar, you must know the electronegativity of an atom. An atom is non-polar if the electrons are shared equally and have a difference in electronegativity that is greater than 0.4. An atom is polar if the electrons are shared unequally and the difference in electronegativity ranges from 0.4 -1.8. What are the important electronegativity’s of some atoms?
Na: sodium (0.93); H: hydrogen (2.20); C: carbon (2.55); N: nitrogen (3.04); Cl: chlorine (3.16); O: oxygen (3.44)
Na H C N Cl O
Give some examples of non polar and polar molecules.
Non polar: C-C, C-H, O-Cl,
Polar: O-C, N-O, N-H, O-H
How are hydrogen bonds formed?
T or F. Hydrogen bonds are represented with a dashed line in a model.
True.
What are the properties shared by many chemical reactions that occur in cells?
1) They require a catalyst. 2) They require energy. 3) They tend to proceed toward equilibrium.
Which molecules readily dissolve in water? And what is this property called?
Ions and polar molecules readily dissolve in water (due to the difference in electronegativity), and they are called HYDROPHILIC. (water loving)
What characteristics describe hydrophobic molecules?
1) they contain many non polar covalent bonds, 2) they are relatively insoluble in water
Briefly describe the characteristics of water in its three states: solid, liquid, and gas. Describe their motion, describe the speed of the hydrogen bond breakage, and explain whether or not they bond is more or less stable.
Ice: water molecules are less likely to move apart and the rate of hydrogen bond breakage SLOWS; therefore hydrogen bonds are MORE stable, and are packed into an orderly formation
Water: water molecules are in rapid motion; hydrogen bonds CONTINUALLY break and re-form; hydrogen bonds are LESS stable than the solid form
Gas: water molecules increase in motion; hydrogen bonds are broken MORE readily, and hydrogen bonds are EVEN LESS stable than the water form
Briefly list the important functions of water.
Participates in chemical reactions, provides support, removes waste, uses evaporative cooling, cohesion and adhesion, surface tension, and lubrication.
